1. Field of the Invention
The present invention relates to a process for the polymerization of vinyl chloride which is characterized by coating prior to polymerization the inside surfaces of a polymerization reactor with a specified reaction product which is obtained by the reaction of a phenolic compound and an aromatic aldehyde. More particularly, it pertains to a process for preventing polymer scales deposition in which in the polymerization of vinyl chloride, polymer scales are prevented by the coating of the foregoing compound from depositing onto the surfaces of the polymerization reactor, agitator blades, baffle plates, a reflux condenser with which the polymerization reactor is equipped, and nozzles of pipes arranged.
2. Description of the Prior Art
In the suspension polymerization of vinyl chloride alone or a monomeric mixture of vinyl chloride as a major component and other monomers copolymerizable therewith as a minor component in an aqueous reaction medium in the presence of a suspending agent and an oil-soluble catalyst, the emulsion polymerization in the presence of an emulsifying agent and a water-soluble catalyst or the bulk polymerization in a liquid or gaseous phase, there is brought about a problem that polymer scales are formed and deposited onto the surfaces of the polymerization reactor, the reflux condenser, nozzles of pipes arranged and the like. The polymer scales deposition invites numerous disadvantages including, for example, decrease the efficiency of heat conduction of the polymerization reactor, decrease of polymer yield, decrease of properties of the polymer product due to fish eyes caused by intermixing of polymer scales peeled off, blockade of the reflux condenser, and nozzles of pipes arranged, and decrease in the operation efficiency of the polymerization reactor due to a great deal of labor and time required for the removal of such polymer scales.
In order to solve these problems, many processes have been proposed for preventing formation and deposition of polymer scales, but they possess merits and demerits and thus a practically satisfactory scales prevention process has never been proposed.
In an attempt to overcome the problems, the present inventors have synthesized a variety of compounds and studied the scales prevention effect thereon in the suspension polymerization, emulsion polymerization or bulk polymerization to thereby find out that a specific class of reaction products obtained by the reaction of a phenolic compound and an aromatic aldehyde produces an outstanding effect of polymer scales prevention.